tModLoader Multiplayer Not Working? Connection & Mod Sync Fixes

Why tModLoader Multiplayer Is Not Working (And How to Fix It)

Few things frustrate a modded Terraria group more than getting everyone on the same Calamity build and then watching the game hang on "Syncing Mods" or quietly refuse every connection. tModLoader multiplayer fails for a small, predictable set of reasons, and almost all of them come down to one of three things: Steam misreading which game is open, mod versions not matching, or a port that never gets through your network. This guide walks through each cause with the exact fix, and explains why running a tModLoader dedicated server removes most of these headaches entirely.

Fix 1: "Steam thinks I have Terraria open, not tModLoader"

This is the single most common complaint. When you launch tModLoader, it starts the base Terraria process alongside it. Because Terraria was the most recent app Steam registered, your status reads "Playing Terraria" and the Steam "Join Game" button points your friend at vanilla Terraria, where your modded world does not exist.

Workarounds that reliably help:

1. Use Steam Invite from inside tModLoader. Host the world through the tModLoader main menu (Multiplayer → Host & Play), then open the Steam overlay (Shift+Tab) and invite your friend from there rather than from the desktop friends list.
2. Launch order workaround. Several players report that opening Terraria first, waiting for it to load, then launching tModLoader and closing the vanilla window leaves Steam pointed at tModLoader. This is fiddly but works when the overlay invite fails.
3. Join by IP instead. Skip Steam matchmaking altogether: host the world, give your friends your IP and port, and have them use Multiplayer → Join via IP.

On a hosted dedicated server this problem disappears completely, because nobody is hosting through their Steam client. Players simply connect to a fixed address.

Fix 2: Stuck on "Syncing Mods" or "Found Server"

When the host hangs on Syncing Mods, or a joining player sits forever on Found Server, the cause is almost always a mod set that does not line up between the two machines. tModLoader will not start a session until both sides agree on every enabled mod.

• Match mods exactly. Every player needs the same mods enabled and the same version of each. A friend running Calamity 2.0.4.1 cannot join a host on 2.0.4.2.
• Reload after any change. Toggling a mod on or off only takes effect after you click Reload Mods. Forgetting this is a frequent cause of a silent desync.
• Share a Mod Pack. The cleanest fix is the host creating a Mod Pack (Workshop → Mod Packs → Save Enabled as New Mod Pack) and sharing the pack folder from Documents\My Games\Terraria\tModLoader\ModPacks\. Everyone loads the identical pack, which guarantees the versions match.
• Disable mods one at a time. If the sync still hangs with matched versions, a single broken or large mod is the culprit. Test with all mods off, confirm a clean session works, then re-enable in small batches.

Fix 3: Port 7777 and network issues

If the host loads fine but nobody can reach it, the connection is being blocked before it arrives. Both Terraria and tModLoader default to TCP port 7777.

1. Forward the port. For self-hosting, forward TCP 7777 on your router to your PC's local IP address.
2. Allow it through the firewall. Make sure every tModLoader.exe and dotnet process is permitted in your firewall and antivirus. A blocked executable produces a silent "lost connection".
3. Check for a port clash. If another program already uses 7777, no connection can complete. Close it, or change the server port in your config.
4. Hand out the right address. Friends on the internet need your external IP (and the forwarded port), not your local 192.168.x.x address.

Setting up mods on a dedicated server

If you graduate from Host & Play to a real dedicated server, mod loading works a little differently than it does in the client. The server reads two files in its Mods folder:

• install.txt lists the Workshop mod IDs the server should download. With no install.txt, no mods install.
• enabled.json lists the mods to actually enable, one quoted name per line inside square brackets. With no enabled.json, no mods turn on even if they are installed.

The simplest route is to build your Mod Pack in the client, then copy the .tmod files, install.txt, and enabled.json from your pack folder into the server's Mods directory. After that, every joining player just needs the same pack locally so the sync passes. The official tModLoader "Starting a modded server" wiki documents the batch and shell launch scripts in full.

Next Steps

• Enable the tModLoader branch on your server
• Install Calamity, Thorium, and other mods correctly
• Read the logs to pinpoint a failed mod
• Fix lag on large modded worlds
• Back to Terraria Wiki Home

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